code: def test_cls_from_tag():
      assert JAML.cls_from_tag("MyExec") == MyExec
      assert JAML.cls_from_tag("!MyExec") == MyExec
      assert JAML.cls_from_tag("BaseExecutor") == BaseExecutor
      assert JAML.cls_from_tag("Nonexisting") is None
  
imports: import dataclasses
  import os
  import pytest
  import yaml
  from jina import Deployment, Flow, requests
  from jina.constants import __default_executor__
  from jina.excepts import BadConfigSource
  from jina.jaml import JAML, JAMLCompatible
  from jina.serve.executors import BaseExecutor
label_desc: Use image node_id 4 for calling a global function with example usage: test_cls_from_tag() without return types